ARM: shmobile: Add forward declaration of struct clk to silence warning

arch/arm/mach-shmobile/board-genmai-reference.c:23:0:
arch/arm/mach-shmobile/include/mach/clock.h:19:54: warning: 'struct clk' declared inside parameter list [enabled by default]
arch/arm/mach-shmobile/include/mach/clock.h:19:54: warning: its scope is only this definition or declaration, which is probably not what you want [enabled by default]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/mach-shmobile/include/mach/clock.h

@@ -16,6 +16,7 @@ void shmobile_clk_workaround(const struct clk_name *clks, int nr_clks,
 #else /* CONFIG_COMMON_CLK */
 /* legacy clock implementation */
 
+struct clk;
 unsigned long shmobile_fixed_ratio_clk_recalc(struct clk *clk);
 extern struct sh_clk_ops shmobile_fixed_ratio_clk_ops;